An aircraft fuselage is typically built in sections, which are then assembled to form the fuselage. The fuselage sections often are built at various locations and then transported to an assembly location for final assembly.
The tail-end of a fuselage is typically enclosed by the aft-pressure bulkhead (APB). In certain constructions, the aft-pressure bulkhead is fastened to the adjacent fuselage section using various mounting structures and mechanical fasteners. For example, metallic T-shaped angled brackets, commonly referred to as “T-clips,” are connected to the aft-pressure bulkhead, while composite brackets, commonly referred to as splice angles, are connected to the adjacent fuselage section. The aft pressure bulkhead-to-adjacent fuselage section connection is then made by mechanically fastening (e.g., with bolts) the T-clips to the slice angles.
Typically, the T-clips have pre-drilled bolt or rivet holes machined therein, whereas the splice angles do not. Holes in the splice angle must be machined on site at the time of assembly in order to account for slight variances in the alignment of the fuselage sections. Because the T-clips are mounted on the aircraft body, it is not possible to maneuver large precision drilling machines into place to drill the matching holes on the splice angle, so the holes must be hand-drilled.
No current solution supports automation of the fuselage APB join. Pilot holes in the T-clips are lined up with the slice angles, a power feed driller is used to drill full size holes through both parts, as well as through a carbon shim that has been placed therebetween. With a heavy power feed driller, it can be difficult to gauge whether the guide pin is accurately located prior to engaging the drill to operate. If the guide pin is slightly off, the cutter penetrates the material in the wrong location or direction, requiring that both parts be removed and replaced.
It is undesirable to hand-drill the splice angle holes by using the T-clip holes as a guide. The T-clip holes are machined to high precision. Hand drilling through the T-clip holes may result in the drill contacting the sides of the hole, altering the dimensions of the hole and, possibly, putting the T-clips out of specification and requiring re-approval. Correcting such a mis-drilling requires time-consuming de-burring and cleaning.
Accordingly, there is a need for drilling splice angle holes that perfectly align with T-clip holes, but without the drill coming into contact with the T-clip.